1. Field of the Invention
The present invention relates to a flash unit for a camera, and more particularly to a flash unit that reduces red-eye phenomenon that occurs during flash photography.
2. Description of the Related Art
When a color photograph of a person is taken using an electronic flash unit, a so-called red-eye phenomenon may occur in which the eyes of the person appear bright the red in the picture. The red-eye phenomenon occurs because a flash of an electronic flash unit is reflected by capillary vessels in the retinas of the person's eyes, and the reflected light is recorded on film. The phenomenon is likely to occur in the following cases.
(1) When pupils are dilated because of a dark photographing environment.
(2) When the distance between a luminous portion of the electronic flash unit and an optical axis of a picture-taking lens is short.
It has been conventionally stated that the number of occurrences of red-eye phenomenon is high when the angle provided between the picture-taking lens and a flash emission tube that are focused on by the pupils of a subject is two degrees or less. In particular, in a so-called zoom camera capable of changing magnification, since zoom magnification has increased in recent years, the diameters of the pupils printed after photographing appear large and become more noticeable.
In order to reduce red-eye phenomenon, the distance between the picture-taking lens and the flash emitting portion may be increased. However, in a camera having a large main body, and a camera in which the flash emitting portion is accommodated in the camera and is separated from the picture-taking lens by a predetermined distance only when used, it is necessary to ensure static pressure strength and impact strength of a driving device for the flash emitting portion, thus causing an increase in the number of components and the need for increasing the rigidity of the components. For this reason, a method for electrically reducing red-eye phenomenon has been proposed. For example, a method has been proposed in which a subject is pre-illuminated by a preliminary illuminating light source just before a photograph is taken for the amount of time required to decrease the size of the pupils so as not to be noticeable. Japanese Patent Laid-Open Nos. 3-192234 and 3-192235 propose an arrangement of the above preliminary illuminating light source in the camera. In an electronic flash unit disclosed in these documents, a flash emission tube is surrounded by a reflector comprising a reflecting surface, a protector is provided in front of the reflector to form a flash emitting portion, and a pre-illuminating light source is provided in the flash emitting portion.
FIG. 4 illustrates an example of a conventional electronic flash unit. Referring to FIG. 5, there are provided a reflector 20 having a substantially semicircular (or a semi-elliptic) shape in cross section of which both sides are blocked, a flat protector 21 attached to the reflector 20 to cover the front surface of the reflector, a flash emission tube 22 provided in the inner part of the reflector 20 and fixed between the side surfaces of the reflector 20, and a pre-illuminating light source (a small incandescent lamp) 23 consisting of a lamp or the like attached to a curved surface portion in the reflector 20. According to the electronic flash unit shown in FIG. 4, the pre-illuminating light source 23 is arranged as close to a parabolic focal point of the reflector 20 as possible, whereby light from the pre-illuminating light source 23 is collected, and a subject illuminating brightness can be increased.
FIG. 6 illustrates another example of a conventional electronic flash unit. The conventional electronic flash unit comprises the reflector 20 and the flash emission tube 22 each having the same construction as that of FIG. 5 (the protector 21 is not provided). The pre-illuminating light source 23 is, however, provided on the bottom surface of the reflector 20 that is provided forward of the flash emission tube 22. This construction allows light beams of the pre-illuminating light source 23 to directly reach the subject.